Intake of carbonated beverages has been associated with increased fracture risk

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American Journal of Clinical Nutrition, Vol. 74, No. 3, 343-347, September

2001

© 2001 _American Society for Clinical Nutrition_

(http://www.ajcn.org/misc/terms.shtml)

Carbonated beverages and urinary calcium excretion1,2,3 <NOBR>Robert P and

and <NOBR>Kar

1 From the Creighton University Osteoporosis Research Center, Omaha.

Background: Intake of carbonated beverages has been associated with

increased fracture risk in observational studies. The usual explanation given

is that

one or more of the beverage constituents increase urinary calcium.

Objective: We assessed the short-term effects on urinary calcium excretion of

carbonated beverages of various compositions.

Design: An incomplete random block design was used to study 20–40-y-old women

who customarily consumed 680 mL carbonated beverages daily. Four carbonated

beverages were tested: 2 with caffeine and 2 without. Two contained phosphoric

acid as the acidulant and 2 contained citric acid. The study included one

neutral control (water) and one positive control (skim or chocolate milk).

Serving

size was 567 mL for the carbonated beverages and water and 340 mL for the

milks. Beverages were consumed with a light breakfast after an overnight fast;

no other foods were ingested until urine collection was complete. pH,

titratable and total acidity, sodium, creatinine, and calcium were measured in

2-h

(morning) fasting and 5-h postbeverage urine specimens.

Results: Relative to water, urinary calcium rose significantly only with the

milks and the 2 caffeine-containing beverages. The excess calciuria was 0.25

mmol, about the same as previously reported for caffeine alone. Phosphoric

acid without caffeine produced no excess calciuria; nor did it augment the

calciuria of caffeine.

Conclusions: The excess calciuria associated with consumption of carbonated

beverages is confined to caffeinated beverages. Acidulant type has no acute

effect. Because the caffeine effect is known to be compensated for by reduced

calciuria later in the day, we conclude that the net effect of carbonated

beverage constituents on calcium economy is negligible. The skeletal effects of

carbonated beverage consumption are likely due primarily to milk displacement.

Key Words: Carbonated beverages • colas • caffeine • phosphorus •

phosphoric acid • urinary calcium • acid loading • citric acid •

fracture risk